1. Field of the Invention
The present invention relates to the field of a hydraulic jack, in particular, to a continuously auto lifting and lowering hydraulic jack, and to a hydraulic circuit for a continuously auto lifting and lowering hydraulic jack.
2. Background Art
In the recent years, auto lifting and lowering hydraulic jacks have greatly been developed. However, there are some defects in the current auto lifting and lowering hydraulic jacks, such as large size, complex structure and high cost in manufacture. Most of the auto lifting and lowering jacks have to be activated by means of an external force during lifting and lowering. The Chinese patent application for invention No. 98112325.2, entitled xe2x80x9cAll-automatic device and method for a hydraulic jackxe2x80x9d, discloses a technical solution for transforming a potential energy of a heavy weight into an available kinetic energy so as to achieve all-automatic control. However, the solution fails to solve such a problem that the release of the energy is caused due to operating inadvertently by an operator. And the valve members of the control valves of those hydraulic jacks are required to have a strict position relationship to each other, and therefore the cost of manufacture is relatively high and the structure of a rotatable valve thereof is complex.
An object of the present invention is to provide a continuously auto lifting and lowering hydraulic jack which can accomplish continuously and automatically lifting and lowering cycles without the help of an external force.
Another object of the present invention is to provide a continuously auto lifting and lowering hydraulic jack which is simple in structure, easy to manufacture and convenient for manipulation.
A further object of the present invention is to provide a hydraulic circuit for a continuously auto lifting and lowering hydraulic jack, in which a hydraulic circuit is simplified by the arrangement of controlling valves to achieve a reliable and convenient control.
To realize the objects described above, the present invention provides a continuously auto lifting and lowering hydraulic jack, which comprises a base, an oil pump, a working oil cylinder, a piston, an oil box, an accumulator, a two-position and two-way valve, a dual-controlling check, a pressure-set check and other checks, wherein the two-position and two-way valve, the dual-controlling check and a pressure-set check are arranged in a straight line; a valve bore is formed in the base to serve as a common valve bore for the two-position and two-way valve, the dual-controlling check and the pressure-set check, with valve members of the two-position and two-way valve, the dual-controlling check and the pressure-set check being disposed sequentially in the valve bore in series; a tappet is positioned between the two-position and two-way valve and the dual-controlling check; and a further tappet is positioned between the dual-controlling check and the pressure-set check.
The present invention further provides a hydraulic circuit for a continuously auto lifting and lowering hydraulic jack, and it comprises an oil pump, a working oil cylinder, a piston, an oil box, an accumulator, a two-position and two-way valve, a dual-controlling check, a pressure-set check and other checks. It further includes a first oil line in which the lower chamber of the working oil cylinder communicates fluidly with the oil box through the two-position and two-way valve; a second oil line in which the oil box communicates fluidly with the lower chamber of the working oil cylinder through a check, a third oil line in which the oil box communicates fluidly with the dual-controlling check through successively one of checks; the oil pump and a further check; and a fourth oil line in which the upper chamber of the working oil cylinder communicates fluidly with the oil box through the pressure-set check and the accumulator; the two-position and two-way valve, the dual-controlling valve and the pressure-set check are connected orderly in series, wherein the dual-controlling check is disposed between the first oil line and the fourth oil line to fluid communicate the two oil lines.